RAP and RAS:Where Are We

Where are We Going

Gerald HuberHeritage Research Group

RAP Use

Drivers

Economics◦ RAP reducesinput costs

Environmental◦ Pressureagainstwasting

Environmental Pressure

AASHTO STANDARD

M323SuperpaveVolumetricMix Design

Proposed Changes◦ Ballot Dec 2014

M323 Terminology

Percent RAP◦ Reclaimed Asphalt Pavement Binder Ratio(RAPBR)

◦𝑅𝐴𝑃𝐵𝑅 =𝑃𝑏

𝑅𝐴𝑃𝑥 𝑃𝑅𝐴𝑃

𝑃𝑏𝑡𝑜𝑡𝑎𝑙

M323 Binder Grade Selection

Virgin Binder Grade

X1: Procedure for Estimating Properties of Blended RAP and Virgin Binders

No Change in Grade < 25%

Follow Recommendations X1

>= 25%

FHWA Memo

Premature CrackingReported

FHWA Recommendations

Increasing RAP (and RAS)◦ May reduce cracking resistance

Potential increased aging

BUT

Existing Pavement Condition being Overlaid

Mix Design using Actual Gsb

Quality Assurance Process

Effect of Recycle Content

300oF - 320oF 240oF - 270oF

- Foam Chem

0% - -

20% RAPBR≈ 23% by weight

20% RASBR

≈ 6% Shingle by weight

40% RAPBR≈ 44% by

weight

PG58-28 PG58-28PG58-28

PG64-22

PG64-22

PG64-22 PG64-22

PG58-28

PG64-22

PG64-22

Diffusion

1

10

100 60

1.7

105

Vis

@1

00

C,

Pa.s

shear

Virgin asphalt

acts as a

‘lubricant’

Pavel Kriz

Esso Canada

Diffusion

Happens with Time

1

10

100

1 100 10000

η*,

Pa.

s

Diffusion Time, s

1

10

100

1 100 10000

η*,

Pa.

s

Diffusion Time, s

1

10

100

1 100 10000

η*,

Pa.

s

Diffusion Time, s

1

10

100

1 100 10000

η*,

Pa.

s

Diffusion Time, s

RAP

50/50 Blend

Virgin

Diffusion

𝐿𝑦

Pavel Kriz

Esso Canada

Effect of Temperature on Diffusion

Time to equilibrium

Homogenous Blend

Blending by Diffusion

Pavel Kriz

Esso Canada

Diffusion In Practice

Pavel Kriz

Esso Canada

10-4

10-2

100

102

104

0.5

0.6

0.7

0.8

0.9

1

Time, days

* /

* ho

mo

gen

ou

s b

len

d, 10

7 P

a.s

HMA

WMA

100 days

mix

silo

transport

paving

service

Fra

cti

on

of

Ho

mo

gen

ou

s V

isco

sit

y

Time, days

HIGH RAP Workshop

Sponsored by◦ Dutch Ministry of Transport

◦ TU Delft

Current Practice◦ High MINIMUM RAP

(50%?)

Theoretical

Practical

Dutch Experience

TU Delft Research

Looking atBlending Zone

Mixing

Occurs by Diffusion

Contractor Visits

Trials at 90%

RAP entry point

into weigh hopper

Contractor 2

JAPAN

NAPA Tour to Japan

High RecycleContent

50% min?

U.S. Experience

RAS

North American Issue

Recycled Asphalt Shingle Use

AASHTO Standards Change

Gradation adjusted finer◦ 95% passing 9.5-mm sieve

Deleterious ◦ Reduced from 3% to 1%

Asphalt Binder Availability Factor◦ Simplified methodology

Future?

Increased RAP and RAS

Increased use of “Rejuvenators”◦ Soft hydrocarbons

◦ Crude oil-based

◦ Bio-based

Continued Research◦ RAP: Reasonably Mature

◦ RAS: More information is needed